Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley
        Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United
        Kingdom.
        Registered in England and Wales under Company Registration No. 3798903
From:   David Howells <dhowells@redhat.com>
In-Reply-To: <CAAUqJDvFuvms55Td1c=XKv6epfRnnP78438nZQ-JKyuCptGBiQ@mail.gmail.com>
References: <CAAUqJDvFuvms55Td1c=XKv6epfRnnP78438nZQ-JKyuCptGBiQ@mail.gmail.com>
To:     =?UTF-8?B?T25kcmVqIE1vc27DocSNZWs=?= <omosnacek@gmail.com>
Cc:     dhowells@redhat.com,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org
Subject: Re: Regression bisected to "crypto: af_alg: Convert af_alg_sendpage() to use MSG_SPLICE_PAGES"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <1506613.1688481248.1@warthog.procyon.org.uk>
Date:   Tue, 04 Jul 2023 15:34:08 +0100
Message-ID: <1506614.1688481248@warthog.procyon.org.uk>
Precedence: bulk

The problem is caused by this bit in af_alg_sendmsg():

		/* use the existing memory in an allocated page */
		if (ctx->merge) {
			sgl = list_entry(ctx->tsgl_list.prev,
					 struct af_alg_tsgl, list);
			sg = sgl->sg + sgl->cur - 1;
			len = min_t(size_t, len,
				    PAGE_SIZE - sg->offset - sg->length);

			err = memcpy_from_msg(page_address(sg_page(sg)) +
					      sg->offset + sg->length,
					      msg, len);
			if (err)
				goto unlock;

			sg->length += len;
			ctx->merge = (sg->offset + sg->length) &
				     (PAGE_SIZE - 1);

			ctx->used += len;
			copied += len;
			size -= len;
			continue;
		}

it doesn't exist in the old af_alg_sendpage() code.  It merges data supplied
by sendmsg() into the last page in the list if there's space.  So we need a
flag to keep track of whether the last page is appendable-to or not.

David